There are a variety of types of applications in which there is a need to control temperatures and/or temperature gradients. One example is that of a person who may need to wear a protective helmet, such as a military or police helmet, a construction helmet, a firefighting helmet, a sports helmet, a motorcycle or other vehicular helmet, or a helmet for any other activity requiring protection for the wearer's head. In some instances, the wearer may be engaged in an activity wherein a significant amount of heat is generated, e.g., running, carrying heavy loads, or participating in a sporting event, and physical duress due to heat may be an issue. A significant amount of generated heat may be given off by a wearer's head, and a helmet having cooling properties may be desirable to increase the amount of heat transferred away from the wearer.